1. Technical Field
The invention relates to a color adjustment apparatus and a computer-readable medium.
2. Related Art
There is a demand for adjusting a specific color in a color image. In a natural image, a flesh color of a person, blue of the sky, and green of grass are called a memory color. For example, it would be more desirable to adjust the memory colors to colors that are preferable to a person who observes the image, rather than reproducing the memory colors with high accuracy. Such an adjustment method of adjusting a specific color involves a higher degree of difficulty than an adjustment method in which a color balance is adjusted for the entire image. Moreover, other methods that employ gradation conversion or a simple formula for calculating a correction may adjust colors other than the specific color to be adjusted.
For example, JP 2004-112694 A (US 2004/0057614 A) describes a color adjustment method in which a specific color, but not limited to the memory color, is adjusted without other colors being affected. FIG. 16 is an explanatory diagram showing an example of a color adjustment method of the related art. In the example shown in FIG. 16, an adjustment subject color is adjusted to a target color. When the adjustment subject color is merely adjusted to the target color, discontinuity may occur between the adjusted color and neighboring colors. To prevent such discontinuity, a subspace is set to include the adjustment subject color and the target color, and the color adjustment is performed in accordance with positions of colors in the subspace. Specifically, color continuity is preserved by changing the adjustment subject color to the target color and not changing colors on a boundary of the subspace using a reference vector directing from the adjustment subject color to the target color. Then, movement amounts for other colors are determined, and the color adjustment is performed.
With such a color adjustment, the adjustment subject color can be adjusted to the target color while it is ensured that the colors outside the subspace remain unchanged before and after the color adjustment and that continuity of colors inside the subspace and on the boundary of the subspace. As a result, a color such as blue of the sky or green of grass can be adjusted and reproduced with a color (target color) that is preferable to a person who observes an image without other colors being affected.